Mobile phones, personal digital assistants (“PDAs”), digital cameras, MP3 players, and other portable electronic devices utilize SSL devices (e.g., light emitting diodes (“LEDs”)) for background illumination. SSL devices are also used for signage, indoor lighting, outdoor lighting, and other types of general illumination. FIGS. 1A and 1B are cross-sectional and plan views, respectively, of a conventional SSL device 10 including an LED structure 11 having N-type gallium nitride (GaN) 14, GaN/indium gallium nitride (InGaN) multiple quantum wells (“MQWs”) 16, and P-type GaN 18. The SSL device 10 also includes a first contact 20 at the P-type GaN 18 and a second contact 22 at the N-type GaN 14. The first contact 20 includes a sheet-like structure across the underside of the P-type GaN 18. The second contact 22 includes a plurality of fingers 21 (three are shown for illustration purposes) coupled to one another by a cross member 23 (FIG. 1B). In operation, a continuous or pulsed electrical voltage is applied between the first and second contacts 20 and 22. In response, as electrical current flows from the second contact 22, through the N-type GaN 14, the GaN/InGaN MQWs 16, and the P-type GaN 18 to the first contact 22, the GaN/InGaN MQWs 16 convert a portion of the electrical energy into light. The generated light is extracted from the N-type GaN 14 of the SSL device 10 for illumination and/or other suitable purposes.
SSL devices having contact structures on the front and back surface of the LED structure 11, such as the fingers 21 and the first contact 20 shown in FIGS. 1A and 1B, are known to those skilled in the art as “thin-film” SSL devices. Such thin-film SSL devices have high thermal performance and efficiency. The fingers 21, however, may be opaque and thus block some of the light. For example, according to conventional techniques, the first and second contacts 20 and 22 typically include aluminum, copper, or other opaque conductive materials. As a result, the second contact 22 blocks light generated in areas directly beneath it. These same areas, however, have the highest current density across the SSL device 10 and thus produce the highest intensity of light in the SSL device 10. Consequently, regions with the highest light intensity per unit area also have the lowest probability of extracting light, which reduces light extraction efficiencies. Accordingly, several improvements in increasing current spreading and light extraction efficiency in SSL devices may be desirable.